UraniumWorkSafetyProcedures.pdf

ABANDONED URANIUM MINE SITE WORK SAFETY PROCEDURES

Colorado Division of Reclamation Mining and Safety Inactive Mines Reclamation Program

Draft: December 13, 2012 Revised 7/1/2024

GENERAL

Colorado Inactive Mines Reclamation Program (IMRP) is completing an ever increasing number of uranium mine safety closures in southwest Colorado. The program is also accomplishing environmental remediation projects on behalf of other State and Federal agencies at abandoned uranium mine sites. In an effort to protect the health and safety of IMRP employees, volunteers, contractors and sub-contractors, safety protocols and cultural practices aimed at limiting exposure to radon progeny and to monitor gamma exposure at work sites are required.

It is understood that IMRP employees, and presumably contractors employees, only work at sites that present an elevated risk of radon progeny or gamma radiation hazard, such as abandoned uranium mines, on a seasonal basis for relatively short periods of time. Exposure to elevated radon progeny or gamma radiation at abandoned uranium mines results from exposed ore bearing formations, and from unprocessed ore and waste rock materials located at individual sites, respectively. Milling or refining operations were generally not undertaken at the small operations that typify abandoned Colorado uranium mining facilities. Thus, the radiologic effects of processed or refined ore are not considered in this document.

Abandoned uranium mines present many unique challenges in order to safely complete a mine closure. These mines were developed in sandstone and shale, and generally at a weathered outcrop located on a hillside or cliff. It is recognized by the IMRP and by partner Federal agencies that the immediate physical hazard associated with closure of these entries is greater than the radon hazard presented at these sites. It is the goal of the IMRP to safely accomplish closure of these mines in a manner that minimizes risks presented by radiation hazards and by the physical conditions of these deteriorating mine entries.

All IMRP personnel, biologic or other subsurface researchers, volunteers, contractors and sub-contractors must exercise caution when working at abandoned uranium mines.

Abandoned uranium mines present many unique hazards including elevated radiation levels that need to be recognized and mitigated when performing project development and mine closure work. Safety precautions due to physical hazards above and beyond the radiologic hazards discussed in this document must be taken when evaluating or working at these sites.

Except as otherwise noted, all persons who perform work under the brow or within a shaft where radon progeny content is unknown should assume that, at a minimum, a fitted half face respirator equipped with P100 filters is required. This precaution applies primarily to pre-construction surveys and site assessments by IMRP staff, if applicable.

All exposure limits and thresholds discussed in this document assume that site visitors are not pregnant. Gamma limits may be significantly lower for pregnant women. All IMRP personnel, volunteers, contractors and sub-contractors who are, or suspect that they may be pregnant must notify Senior IMRP staff in advance of arriving at these sites so that appropriate modifications to assigned work or to individual gamma exposure limits may be accommodated.

Alpha (radon and radon progeny) and gamma exposure limits and thresholds are significantly lower for persons under the age of 18 years. No one under the age of 18 years is anticipated to be working or volunteering at these sites. Should this not be the case, Senior IMRP staff must be notified in advance so that appropriate modifications to work or to individual exposure limits may be accommodated.

RADON PROGENY

Limiting Exposure Limiting exposure to radon progeny is dependent upon executing certain cultural practices, particularly during mine closure construction. Limiting or eliminating exposure to the flow of atmosphere from within the mine across the work area is the primary method of limiting exposure through engineering controls. The use of PPE at specified levels of radon progeny exposure has limited applications and should only be used following implementation of engineering controls. Continuous monitoring of radon progeny is required when working at the brow.

Basic Health and Safety Procedures Basic health and safety procedures must be followed when working at abandoned uranium mines. These procedures include:

- Wash hands and face with clean water or disposable wipes before eating, drinking, smoking or using smokeless tobacco;

- Avoid welding under the brow. If welding under the brow is unavoidable, a NIOSH/MSHA approved fitted half-face respirator with new, replaceable P100 filter cartridge(s) must be worn by the welder and others under the brow;

- No smoking within 300 feet of any work location;

- Thoroughly wash clothing and equipment following completion of work activities.

Contractors, IMRP staff and subsurface researchers each have differing responsibilities and health and safety considerations pertaining to their time spent at abandoned uranium mines. In order to accommodate these differences, radon and gamma procedures pertinent to each group are addressed below.

PART 1; PROCEDURES FOR IMRP STAFF

Many different sites are encountered by IMRP staff and potentially contractors during the development and construction of an abandoned uranium mine closure project.

Each site has different attributes, which may include the presence of ore and waste rock, and ventilation characteristics. Further, work at abandoned uranium mines is relatively limited during the course of a work year. Therefore, administrative goals for exposure to elevated radiation have been established for radon progeny and for gamma exposure.

Radon Progeny Safety Procedures

Administrative Controls Administrative controls are the best way to manage IMRP staff exposure to radon progeny-rich atmosphere. IMRP staff maximum exposure to radon progeny-rich atmosphere occurs during project development. The basic closure design tasks which need to be completed under the brow occur during project development. Therefore, the most effective way to minimize exposure is to limit the amount of time staff spends under the brow on a site by site basis. Measurements of interior mine entry dimensions, and evaluation of rock competency need to be accomplished at each mine entry. It is estimated that this work can be accomplished in fifteen minutes or less under the brow at each site. Further, Project Managers should limit their time at the brow and confine their entry into a mine feature to that distance necessary to construct the closure, generally no more than fifteen feet beyond the entry.

IMRP staff is required to keep accurate records that document the number of hours each individual spends working under the brow annually (January 1 through December 31). In no instance should any one staff member accumulate more than 800 hours annually under the brow.

Continuous radon progeny measurements will be made during project construction.

These continuous measurements will begin immediately prior to initiating construction, and will continue until work under the brow is completed. The continuous measurements will be periodically recorded in the Project Manager construction logs and in the contractor’s job log. Contractor will consider the instantaneous continuous measurement to be the exposure level to determine actions required to reduce exposure below the 0.2 Potential Alpha Energy Concentration (PAEC) Working Level threshold.

Sample Methodology

The IMRP calibrated Bladewerx SabreAlert2 radon detector or other suitable alternative method will be used to collect radon progeny samples. Best results are achieved when running the radon detector for fifteen minutes in fresh air prior to work commencing. For adits and declining entries, radon progeny readings will be continuously collected at the mine entry workspace. At shafts or large vents, the Bladewerx SabreAlert2 will be continuously ran at the side of the feature at ground level on the edge of the opening to the extent safe and not endangering health, safety or instrument. For both adits and shafts, continuous monitoring of radon progeny measurements should occur every 15- 30 minutes to ensure radon progeny levels remain below 0.2 Working Levels (NOTE:

the SabreAlert instrument measurements are in milliworking level (mWL) units, therefore 200 mWL are equal to 0.2 WL).

The contractor will record the highest radon level encountered at each feature and report on the contractor daily log form. If levels above 0.2 WL are encountered the contractor must report actions taken to avoid exposure to higher radon levels. NOTE:

Center for Disease Control report cited below recommended 0.1 WL threshold based on a 9-month period (1,500 hours) work exposure. Uranium project implementation work typically is never more than half that amount of time so 0.2 WL is a more realistic level and still very conservative. The report also stated that reference concentration could be adjusted upward based on improved occupancy estimates as long the overall 1.0 Working Level Month (170 hours) is not exceeded.

For ventilation drill holes, the Bladewerx SabreAlert 2 will be placed or suspended immediately above the drill hole so as to minimize the potential for atmospheric contamination of the sample.

Note that for vertical entries and ventilation holes which will be mechanically backfilled using a piece of equipment fitted with an enclosed cab and functional air conditioner creating positive air pressure, radon progeny measurements are not required.

In addition to recording the Working Level measurement, the following will be recorded during the initial entry inventory:

- Site number (to be recorded in Brass Cap data base);

- Mine name, if applicable;

- Weather conditions at the time of sampling (temperature, relative wind conditions, stable or unstable atmospheric conditions);

- Determination of whether entry inhales or exhausts o If mine exhausts, attempt to locate and record ventilation inlet entry and entry-specific data; note relative exhaust velocity;

o If vent inhales, note relative inhalation velocity;

o Attempt to determine whether inhaling or exhausting entries are part of a larger mining complex, and note relationship of one entry to another.

Mine atmosphere movement will be evaluated using an MSHA approved ventilation smoke tube or Regin® Smoke Bottle or similar device. The hand-held smoke device will be activated and observed at the planned location of the closure within the entry.

The device will be manipulated so that the direction of smoke movement may be observed and recorded at each rib, at the floor and at the back.

Construction Measurement

Continuous radon progeny measurements will be made whenever people are working to construct a closure under the brow. This will be accomplished using a Bladework Sabre Alert 2, or equivalent calibrated instrument supplied by IMRP. Instrumentation will be placed at the mine entry when working under the brow and will be active whenever such work is in progress. Project Manager and contractor will periodically check and note the Working Level measurements as construction progresses. The Sabre Alert2 is equipped and programmed with an audible alarm when PAEC chronic concentrations exceed 0.2 Working Levels.

Radon gas is approximately 7.5 times heavier than air so theoretically if the Sabre Alert2 detector is placed on the ground at the entry, it will detect the most concentrated radon progeny levels.

Due to the Sabre Alert2 being battery powered, the contractor must be diligent to recharge the detector at the end of every shift and have onsite a portable battery charging device or generator to allow continuous operation. Work will cease if work at the brow is being performed without the Sabre Alert2 in operation collecting radon progeny measurements.

Due to the dusty nature of the uranium mine environment, the contractor must periodically check and change the air pump inlet paper filters to avoid clogging and accumulation of radon from previous sites. The Project Manager will review the operation of the Sabre Alert2 radon detector at the pre-construction meeting.

In addition to periodically recording radon progeny Working Level measurements during construction, Project Manager and contractor will note whether a change in the air circulation system occurs. Such a change could indicate variations in radon progeny concentration at the work area.

It is the responsibility of the contractor to ensure the radon detector is not placed in areas where damage to the unit might occur and to maintain the unit during the project, especially during transport. The detectors will be provided in a protective hardened case and the contractor must secure the detector at all times when not in use.

If the air circulation system reverses its direction of movement so that the entry exhausts and radon progeny levels exceed 0.2 Working Level, work at the brow will end until sampling of the atmosphere dictates otherwise.

The continuous measurement during construction of radon progeny Working Level will be used to dictate adjustments required to avoid elevated radon progeny working levels.

See construction practices section below.

Note that for entries which will be mechanically backfilled using a piece of equipment fitted with an enclosed cab and functional air conditioner creating positive pressure, continuous radon progeny measurements are not required.

Radon Progeny Exposure Limitation – Not to exceed 1.00 Working Level Months per year (assumes 170-hour month). Requirements based on annual accumulated exposure times not to exceed 800 hours for IMRP staff and 1,000 hours for contractor staff. Note special PPE requirements for subsurface researchers on page 9 of this document.

PART 2; CONTRACTOR SHEAP AND CONSTRUCTION REQUIREMENTS

Contractors should note that radon progeny concentrations are expected to change over time, sometimes becoming greater, other times becoming less. Appropriate construction practices will be required as radon progeny concentrations change during the progression of work; therefore, it is not anticipated that a change in required mitigation constitutes a changed condition.

Construction Practices to Reduce Radon Progeny Exposure

Entries where continuous measurements during construction record radon progeny increasing above 0.2 Working Levels the contractor must stop construction and implement one or more construction practices before continuation of work.

The purpose of implementing construction practices is to minimize or prevent the flow of radon-progeny contaminated atmosphere across the mine safety closure work area.

Due to physical (non-radiation related) safety considerations at individual mine entries, and variations in equipment availability, contractor, subject to Project Manager approval, may choose which construction practices to implement.

Recommended construction practices include, but may not be limited to the following:

Elimination of Mine Atmosphere Flow Through the Construction Area.

In an attempt to limit radon progeny exposure when conducting mine closure activities, it is beneficial to have an understanding of the natural mine ventilation system, assuming that one exists. Therefore, it is important to take note of whether entries or vents inhale or exhaust, and how they react to changes in atmospheric pressure, should the opportunity arise.

In order to minimize the flow of air from inside to outside a mine entry location during construction of a safety closure, the pre-construction movement of atmosphere will have been assessed, so that the air circulation pattern may be used to reduce potential radon progeny exposure to work crews. Pre-construction atmospheric circulation patterns, if any were observed, will have been noted in the construction bid specifications.

Elimination or minimization of atmosphere flow may be accomplished at entries that exhaust by identifying ventilation drill holes or shafts, and preferentially sealing those features to eliminate or greatly reduce the flow of atmosphere through the mine.

If atmosphere is observed to move from inside to outside the entry (mine exhausts), attempt to locate a ventilation shaft or entry. Seal or otherwise close the in-taking ventilation feature prior to beginning any construction at the exhausting entry. If the ventilation shaft is sealed, the mine atmosphere flow at the entry should be significantly reduced while the mine closure is completed.

Conversely, if atmosphere is observed to move from outside to inside the entry (mine inhales), attempt to locate a ventilation shaft or entry. Close the mine entry per construction specifications prior to beginning any construction at the ventilation feature.

If the entry is sealed, the mine atmosphere flow at the ventilation shaft should be significantly reduced while the ventilation feature closure is completed.

Engineering Controls.

Engineered controls include simple barriers to atmospheric flow through the construction area which are erected by contractors inby the work zone. Atmospheric barriers may include brattice cloth which is securely braced to the ribs, back and floor to prevent or minimize the movement of atmosphere from deeper in the mine. Barriers may also be constructed of inflatable mattresses, balloons or similar materials which conform to the margins of the mine. These materials must be removable upon completion of all closures excepting hand backfills, in which case they may be left in place following construction completion.

Another engineered control is to provide for fresh air dilution of radon progeny at the work area. A generator powered fan may be provided so that fresh air is directed across the work area. Sufficient air must be delivered to the work area so that dilution of radon progeny to below 0.2 Working Level is achieved.

Excessive fugitive dust must be monitored during backfilling activities, footer excavation or other operations requiring moving ore, waste rock or other earthen materials within the entry, so that excessive dust is not generated during operations. Watering of cut/fill areas may be necessary during periods of excessive dust, especially if elevated gamma concentrations have been documented.

Following completion of the project, all equipment provided by contractor must be thoroughly washed.

Administrative Controls.

Administrative controls involve utilization of the work crew in a manner that maximizes productivity, while minimizing time under the brow. Administrative controls are required to be implemented under the IMRP SHEAP by all contractors working at abandoned uranium mines.

Minimizing time under the brow, which equates to minimizing duration of exposure, can be accomplished by carefully planning the construction sequence of the specified closure. Complete as much work as possible outside the entry when installing grates and culvert closures. Pre-stage appropriate quantities of materials to complete bulkheads in an efficient and expeditious manner that reduces exposure time (time under the brow). Rotate individuals or work crews during the course of completing a closure in order that individual exposure times are minimized, while distributing the reduced exposure throughout the crew.

Experience has shown working in the fall of the year, typically when projects occur based on NEPA requirements, lessens the likelihood of more frequent and active weather patterns occurring. Also, on sites where radon progeny has been elevated, working in the early morning hours has provided a window for less exposure to work crews.

Contractor is required to keep accurate records that document the number of hours each crew member spends working under the brow annually (January 1 through December 31). In no instance may any one crew member accumulate more than 1,000 hours annually under the brow.

Personal Protection Equipment.

Personal Protection Equipment, generally in the form of NIOSH/MSHA approved fitted half-face respirator with new, replaceable P100 filter cartridge(s) will be utilized during any welding activities under the brow.

Contractors and all work crews will be provided with the report cited below defining the effects of radon exposure and the evaluations used for recommendations to reduce worker safety hazards.

Evaluation of Exposure to Radon Progeny During Closure of Inactive Uranium Mines – Colorado. Robert Daniels, PhD, CHP and David C. Sylvain, MS, CIH. Health Hazard Evaluation Report, HETA 2011-0090-3161, July 2012.

PART 3; UNDERGROUND RESEARCH AND INVESTIGATIONS

Bat habitat and other researchers, including IMRP staff, who enter abandoned underground uranium mines beyond the closure construction zone are likely exposed to greater radon progeny concentrations per visit as a result of traveling to the far reaches of these mines. It is expected that radon progeny concentration increases dramatically with distance from the entry.

In order to protect long term health and safety of underground researchers, full self contained breathing apparatus is required for entry beyond fifteen feet into abandoned uranium mines by volunteers, State employees, contractors or others working at the request of the Division of Reclamation, Mining and Safety, Inactive Mines Reclamation Program.

GAMMA

The risk of gamma exposure exists when working at areas that contain remnant uranium or vanadium ore or waste rock materials, therefore, the potential for gamma exposure exists at most abandoned uranium mine sites. Earthwork such as stream channel construction, waste pile relocation and similar work, including mechanical and hand backfilling of a mine entry with mine waste, are potential exposure conditions, as individuals may be working in direct contact with remnant ore or waste rock.

IMRP Staff

For projects requiring excavation of mine benches, ore stockpiles or mine waste to facilitate environmental remediation work, a gamma survey of all potentially affected areas must be made. To do so, the affected area will be surveyed, making measurements in an appropriate pattern when walking the affected area. The data and data point location (when possible) will be recorded. At larger environmental restoration projects, Global Positioning System technology will be used to map and flag the perimeter of the area affected by earthwork operations. During construction, periodic monitoring of the excavated material will be made to evaluate changes in gamma as excavation proceeds.

The U.S. Department of Energy, Defense Related Uranium Mine (DRUM) program Verification and Validation inventory reports collect gamma surveys for all waste rock piles utilizing a GPS system. IMRP staff will review these gamma surveys and inform the contractor of sites with elevated gamma measurements. Typically the levels recorded are below 256 µRrem/hr (screening value equal to 100 mrem exposure for 2-week recreational camping scenario).

Affected staff will be issued a personal dosimeter. Once issued, the device must be worn at all times when on-site during any of the activities tabulated above.

When conducting work as described above, IMRP staff will complete the following:

- Report the dosimeter readings every six months or immediately if approaching

2 rem/year dosage.

- The administrative goal is to receive a calculated gamma dose equal to or less than 2 rem/year.

The intent of the semi-annual reporting is to provide a method to monitor accumulated exposures so that individual exposures can be tracked over time to ensure that the administrative goal is not exceeded. Report the potential of approaching the exposure limitation to Senior Staff immediately upon becoming aware that the potential to exceed the limitation exists from the dosimeter reading. Current (2024) EPA and OSHA annual gamma exposure thresholds are 5 rem/year.

Contractor Staff IMRP will use a scintillometer to conduct a general gamma survey of each closure location, and publish a range of ambient gamma data for each work site in the construction bid specifications, when applicable. Periodic monitoring of each work location during construction to evaluate changes in gamma may occur if earth work activities, particularly generation of fill for backfill and significant ground surface modification occurs.

It is the responsibility of Contractor to monitor the exposure of each of their employees and sub-contractors. Contractor must keep a daily log that records site name / number;

employee (including sub-contractor) name and time on location for each individual.

Accumulated daily gamma exposure levels are to reported for each member of the work crew on the contractor daily log.

IMRP approved personal dosimetry will be issued to Contractor for distribution to employees or sub-contractors, it is the responsibility of contractor to ensure proper use and that individuals use only the assigned dosimetry during their time on site.

At a minimum the dosimeter must meet the following specifications:

The dosimeter must be portable in size as to be worn by individual workers and be powered by common replaceable batteries (AA or AAA). The dosimeter must be capable of reading gamma radiation in the range of 0.1 mrem (millirems) to 5 Rem or above and displayed in visible digital readout. Preferably units would include an alarm to alert users of high exposure levels.

DRMS uses a RADOS brand RAD60 which includes an alarm and the ability to switch between dose and dose rate for measuring gamma on site. Although not required to purchase the RAD 60 if additional units are necessary, they can be purchased from Laurus Systems at www.LaurusSystems.com .

‘Pencil’ type dosimeters or similar models that do not have a real time digital readout or require an external power supply are prohibited.

Project Manager will review the RAD 60 dosimeter operations and correct settings at the pre-construction meeting. Contractors are required to collect time-on-site data for each crew member, and to make dose calculations using the gamma data provide by Project Manager. The time data and dose calculation for each crew member must be kept on-site and available for inspection by Project Manager during the course of the project. Weekly dosimeter readings must be recorded on the daily work sheet at the end of each work week.

It is the responsibility of Contractor to reassign employees and sub-contractors who are approaching the exposure limitation described below, so that no further exposure results from continued work at the Project. It is the responsibility of Contractor to ensure dosimeters are worn during project work only and possible invalid external exposures do not cause elevated dosimeter values unrelated to work exposures.

Gamma Exposure Limitation – Not to exceed 2 rem annually.

The CONTRACTOR should provide a signature block similar to the one below that each employee can sign to verify that they have read and understand the safety aspects of the project and accept the provisions of the SHEAP.

http://www.laurussystems.com/

The above information was reviewed, received, and understood.

Contractor Representative:

Signature Date

Employee: